$def with(openstax_id)

$ url = 'https://openstax.org/details/books/' + openstax_id

<hr>
<div class="cta-section">
  <p class="cta-section-title">$_("Download Options")</p>
    <ul class="ebook-download-options">
      <li><a href="$url" title="$_('Download PDF from OpenStax')">$_("PDF")</a></li>
      <li><a href="$url">$_("More at OpenStax")</a></li>
    </ul>
</div>
